JPH01228613A - Manufacture of pipe with external fin - Google Patents

Abstract

PURPOSE:To form fins having high heights in one path and to prevent inner surface defects by positioning the intersection point of the load acting line of the adjacent roll flange on the outside of a critical point placed inside by proportion to the thickness of the pipe after working from the peripheral surface of the inner surface control tool. CONSTITUTION:Caliber rolls 3, 3... are disposed peripherally in the state of positioning the rotating shafts 2 to be on the same plane orthogonal to the path center of the pipe 1 to be worked. The inscribing circle of the caliber rolls 3, 3... has the diameter according with the outer diameter of an after- worked pipe 1 to be rolled and the clearances G between roll flanges are in accord with the thickness of the fins 5 to be formed. The intersection point P by the load acting lines L, L of the adjacent roll flanges 7, 7 (the intersection point of the extension lines in the diameter direction of the roll flanges) is positioned outside the critical point placed inside by the thickness of the pipe after working from the outer peripheral surface of the inner surface control tool. By this method, the defect of the inner surface at the fin part is prevented to obtain economically the high quality pipe with external fins.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the manufacture of a tube with external fins, which allows a tube having three or more fins parallel to the tube axis on its outer circumferential surface to be manufactured in one bath without any pre-processing. .

[Conventional technology]

This kind of externally finned tube used as a heat transfer tube of a heat exchanger is often manufactured by extrusion or drawing using a die. However, these methods have low efficiency.

For example, the method using die drawing requires a large processing force and the amount of processing per pass cannot be large, so in order to secure the required fin height, processing of at least two buses is usually required, which reduces manufacturing efficiency. decrease. Therefore, processing using rolls can be considered.

As a method for manufacturing a tube with external fins using a roll, the method shown in JP-A-57-142715 and the method shown in JP-A-60-170525 are known.

[Problem to be solved by the invention]

011's method involves rolling down the pipe to be processed l using three or more rolls 3', 3', etc. placed around the pass center of the pipe to be processed with a predetermined gap. Perform processing. Fins 5 are formed in the gaps between the rolls by rolling down. However, since this method does not use an inner surface regulating tool for the pipe to be processed l, there is no substantial change in the wall thickness of the pipe to be processed l before and after processing, and the fins 5 are placed on the outer surface of the pipe as shown in the figure. Even if a grooved roll is used, the fin 5 has a folded shape 6', which inevitably causes a crease 6 on the inner surface of the tube. If folds 6' or shrinkage 6 occur in the tube, when the tube is used as a heat transfer tube by passing water inside, water scale or the like may accumulate in this portion, inhibiting heat transfer and causing corrosion. Furthermore, in this method, the flange-corresponding portion of the roll 3' and the top of the fin 5 are subjected to bending, resulting in locally thin walls and a decrease in strength.

In the latter method, the tube to be processed is rolled in the circumferential direction using transfer rolls that have irregularities formed on the outer circumferential surface, and fins are applied to the outer circumferential surface of the tube to be processed. This results in an increase in the scale of the equipment, such as the need for additional equipment. Furthermore, this method is conventional in that fins are formed on the inner and outer surfaces, and if the fins are formed only on the outer surface, the dimensional accuracy of the inner surface of the tube becomes unstable. Furthermore, there is a restriction that only fine pitch fins can be formed.

In view of this situation, the present invention provides a tube with external fins suitable for a heat transfer tube having three or more fins with relatively large gaps, without rotating the tube to be processed, and without causing bending or shrinkage on the inner surface of the tube. The purpose of the present invention is to provide a method that can be efficiently manufactured in one processing step.

[Means to solve the problem]

In order to achieve this objective, the present inventors created three or more hole shapes around the pass center O of the pipe to be processed l, each having a rotation axis 2 perpendicular to the pass center O, as shown in FIG. The rolls 3, 3... are arranged around the circumference with a predetermined gap G, and while the pipe to be processed l is restricted from the inside with the inner surface regulating tool 4, the grooved rolls 3, 3... are applied in the centripetal direction. We devised a method to move the compressed tube in the axial direction.

If the pipe to be processed 1 is pressurized in the centripetal direction from the outer side with three or more grooved rolls 3, 3, etc., and the pipe to be processed l is restricted on the inner side by the inner surface regulating tool 4, the pipe to be processed 1 is is thinned, and a part of the thinned meat is adjacent to the hole-shaped rolls 3, 3.
The metal flow bulges out from G between the flanges, and a fin 5 that is completely integrated with the tube body and has no folds is formed on the outer peripheral surface of the tube to be processed in the tube axis direction, resulting in a shrinkage 6.
can be expected to be prevented.

However, research conducted by the present inventors has revealed that this method cannot completely prevent shrinkage 6. According to the investigation by the present inventors, three or more grooved rolls 3, 3...
Even if thinning is caused in the pipe to be processed l by the inner surface regulating tool 4, the intersection point P of the load action line L of the adjacent roll flange 7. ), a shrinkage 6 may occur depending on the position of It turned out that it needed to be done.

The method for manufacturing a tube with external fins of the present invention was developed based on such knowledge, and consists of three or more grooved rolls 3, 3...
When forming the fins 5 in the tube axis direction by reducing the wall thickness of the tube 1 to be processed using the inner surface regulating tool 4 and the fin 5 in the tube axis direction, the intersection point P is positioned outside the critical point P0.

[For production]

Figure 1 shows three grooved rolls 3, 3.3 and an inner surface regulating tool 4.
This figure illustrates changes in the formation status of the fins 5 based on changes in the position of the intersection point P when thinning the pipe to be processed l and forming fins in the tube axis direction.

CaseA shown in FIG. 1 is when the intersection point P is located on the outside of the outer peripheral surface of the inner surface regulating tool 4, and Ca5eB is when the intersection point P is located on the outer peripheral surface of the inner surface regulating tool 4.
Cas ec indicates the case where the intersection P is located inside the outer peripheral surface of the inner surface regulating tool 4.

In Ca5eA, since the intersection point P exists inside the material of the pipe to be processed 1, the force toward the center of the pipe to be processed 1, which is the resultant force of the load of the adjacent roll flange (indicated by the white arrow), is at the intersection point. m Ca that acts on P and does not cause a drawdown 6
s e B is a state that indicates a theoretical limit that does not cause this drawdown 6 to occur.

On the other hand, in Ca5eC, since the resultant force that suppresses the shrinkage 6 is not generated in the material of the pipe to be processed 1, the shrinkage 6 is theoretically generated. However, in reality, since the pipe to be processed l is integral in the circumferential direction, deformation occurs even in the peripheral portion in the opening direction of the portion that is forcibly deformed, following the portion that is forcibly deformed.

Therefore, even if the intersection point P is located inside the outer circumferential surface of the inner surface regulating tool 4, the shrinkage 6 can be prevented as long as the distance from the outer circumferential surface is within a certain range. The inventors' research has revealed that the critical distance from the outer circumferential surface that can prevent this shrinkage 6 depends on the deformability of the material, but is usually the wall thickness t of the pipe to be processed 1 after processing. Ta.

Therefore, in the method of the present invention, the intersection point P is located outside the critical point P0.

FIG. 2 shows a case where the shrinkage 6 remains even though the intersection point P is located outside the outer peripheral surface of the inner surface regulating tool 4.

CasθD shown in FIG.
This is a case where only the dark direction narrowing of the pipe to be processed l is performed. In this case, since the intersection point P is not located within the material of the pipe to be processed l, the shrinkage 6 will inevitably occur. does not occur.

Ca5eE is a case where the degree of outer diameter reduction is extremely large. If the degree of outer diameter reduction is extremely large, the axial elongation will outweigh the material flow induced in the I+51 direction, and the fin 5 portion will elongate following the axial elongation of the material directly below the roll. In such a state, even if the intersection point P is on the outside of the outer circumferential surface of the inner surface regulating tool 4, the force acting on the intersection point P is reduced and the occurrence of 6 cannot be prevented.According to the investigation by the present inventors,
If the outer diameter of the pipe I after processing is smaller than the inner diameter before processing, shrinkage 6 cannot be prevented even if the intersection point P is outside the critical point P0.The method of the present invention is effective because the This is a case where the outer diameter of the processed pipe l after processing is larger than the inner diameter before processing.

FIG. 3 shows a case where there are two grooved rolls 3. In this case, the fins 5 are generated by the metal flow in the circumferential direction of the pipe to be processed 1, but although the intersection point P is located within the main body material of the pipe to be processed l, there is a fin at the intersection P toward the center of the pipe to be processed l. No resultant force is generated and sink mark 6 occurs. Therefore, the method of the present invention is limited to the case where three or more grooved rolls 3, 3, . . . are used.

[Example] In carrying out the method of the present invention, a grooved roll 3.
3... are installed around the circumference with the rotating shaft 2 positioned on the same plane perpendicular to the path center of the pipe to be processed l.

The inscribed circles of the grooved rolls 3, 3, . . . have a diameter that matches the outer diameter of the pipe to be processed 1 after processing, and the gap G between the roll flanges matches the thickness of the fin 5 to be formed.

Further, in order to cause thinning of the pipe to be processed l, the gap between the inscribed circle and the inner surface regulating tool needs to be smaller than the wall thickness of the pipe to be processed l before processing.

However, the diameter of the inscribed circle needs to be larger than the inner diameter of the processed pipe 06 of the pipe to be processed l. This is because, as described above, if an extreme reduction in the outer diameter is applied such that the outer diameter of the pipe to be processed l after processing becomes smaller than the inner diameter before processing, shrinkage 6 will occur.

The grooved rolls 3.3... may be arranged in one stage or in multiple stages in the l-pass.

The number of passes is basically one pass, but if the material is difficult to process or the fin height is to be increased, multiple passes may be performed.

The grooved rolls 3, 3... may also be driven or not driven. In the case of drive, it is a rolling process, and in the case of non-drive, it is necessary to apply pipe feeding force from the outside like drawing.

According to the method of the present invention, the tips of the fins 5 are rounded because they are free surfaces. When it is necessary to finish the fins 5 to have a rectangular cross section, after forming the fins 5, finishing processing may be performed by drawing with a die or the like.

Further, irregularities in the circumferential direction may be formed on the outer peripheral surface of the inner surface regulating tool 4, and in this case, 1! of the tube with inner and outer fins. ! ! 6 Four non-driven grooved rolls shown in Fig. 4 are installed around the roll flanges with a gap of 10.0 m and an inscribed circle diameter of 70-1. By inserting a carbon steel pipe with an outer diameter of 86mm, an inner diameter of 54mm, and a wall thickness of 16m5 between the internal regulating tool (plug) and the inner and outer diameters with lubrication, four fins in the tube axis direction were formed on the outer circumferential surface of the steel pipe. .

As a result of forming four fins on each of five steel pipes in this way, the rolls opened due to the roll reaction force during processing, and the outer diameter of the main tube was 70.5 am, but the outer diameter of the fin was 82. l~
An outer diameter of 82.9 *** was obtained, and a peak height of 5.8 to 6,
2-2 was secured, and no shrinkage occurred on the inner surface. The position of the intersection P was 6.25 Wafl from the outer peripheral surface of the plug.

〔Effect of the invention〕

The method for manufacturing a tube with external fins of the present invention applies thinning processing to a tube to be processed using a combination of a grooved roll and an inner surface regulating tool, thereby forming a fin with a large peak height in one bath, and reducing the thickness of the tube. Prevents the inner surface of the fin from shrinking, which is a problem when processing. Furthermore, since the tube to be processed does not require rotation, the scale of the apparatus is small and a good inner shape can be obtained. Therefore, the method of the present invention economically produces a high-quality externally finned tube and is highly effective in reducing manufacturing costs.

[Brief explanation of the drawing]

Figures 1 to 3 are schematic diagrams showing changes in the fin formation situation depending on the roll position when manufacturing a tube with external fins using a grooved roll and an inner surface regulating tool, and Figure 4 is used in an example of the present invention. A front view of the roll showing the shape and dimensions of the grooved roll,
FIG. 5 is a schematic diagram showing the state of fin formation when the conventional inner surface regulating tool is not used. In the figure, l: pipe to be processed, 2: rotating shaft, 3: grooved roll, 4
;Inner surface regulation tool, 5: Fin, 6: Draw. Fig. 1 aseC Fig. 2 1”<J aseE Fig. 3 Rod 5 Fig.

Claims (1)

[Claims] 1. Three or more hole-shaped rolls with rotational axes perpendicular to the pass center are placed around the pass center of the pipe to be processed with a predetermined gap, and the rolls are regulated from the inside of the pipe using an inner surface regulation tool. The pipe to be processed passes through the grooved roll while being pressurized and thinned in the centripetal direction by the grooved roll, and a part of the reduced thickness bulges out between the flanges of the grooved roll to form the pipe to be processed. When forming a fin in the tube axis direction on the outer periphery of the pipe, the intersection point P of the load action line of the adjacent roll flange is set at a critical point P_0 that is inward from the outer circumferential surface of the inner surface regulating tool by the thickness of the pipe after processing.
A method for manufacturing a tube with external fins, characterized in that the tubes are located further outward.